PVB Film for Composite Safety Glass and Composite Safety Glass

ABSTRACT

Composite glass with films based on partially acetalated polyvinyl alcohol containing a softening agent, especially PVB based, as an intermediate layer with magnesium salts or calcium salts of organic acids as an adhesion-reducing additive (anti-adhesive agent) exhibit large amounts of fluctions with regard to adhesion when the composite glass is subjected to thermal stress. According to the invention, phosphorous compounds are used, selected from the group consisting of organophosphites i.e. esters of phosphorinic acid with organic radicals, organophosphates, i.e. esters of orthonophosphoric acid, as an additive which during further processing compensates for fluctations in adhesion in films based on partially acetalated polyvinyl alcohol containing a softening agent. The invention is used in the production of films for the manufacture of safety glass, especially used in the building and automotive industry.

TECHNICAL FIELD

The invention relates to a plasticized film composed of partiallyacetalized polyvinyl alcohols as intermediate layer in laminated safetyglass.

Laminated safety panes, composed of two glass panes and of an adhesivefilm composed of partially acetalized polyvinyl alcohols, preferably ofpolyvinyl butyral (PVB), and bonding the glass panes are in particularused as windshields in motor vehicles, where, if appropriate, one glasspane may have been replaced by a plastics pane, mainly composed of anamorphous polyamide, transparent PMMA, polycarbonate, or polyester.Silicate glass/silicate glass or silicate glass/plastics laminates ofthis type are also used in the construction sector, e.g. as windowpanesor as partition walls, and, if appropriate and depending on the use ofthe laminates, e.g. as bulletproof glass, use is also made of multiplelaminates, i.e. laminates which are composed of more than twoload-bearing layers.

As is known, the safety properties of laminated glass with a polyvinylbutyral film (PVB film) depend on the adhesion between film and glass.If the adhesion is very high, although the glass fragments are sure toadhere to the film in the event of mechanical failure of the laminatedglass—e.g. through exposure to impact—thus preventing the separation ofsharp-edged glass splinters, it is relatively easy for an impactingobject to penetrate the laminated glass, because the strong adhesion ofthe PVB film to the glass is such that the film can undergo very littleelastic deformation at the impact point, and therefore also contributesonly little to the deceleration of the object. If the adhesion to theglass is lower, the PVB film can deform and separate from the glass whensubjected to tensile stress at the impact point, the result beingdeceleration of the impacting object.

The plasticizers for PVB which are used commercially in conventional PVBfilms comprise mainly aliphatic diesters of tri- or tetraethyleneglycol. Among these are 3GH, 3G7, and also 4G7, in all of which theprefixed numeral refers to the number n of the oligoethylene glycolrepeat unit H—(O—CH₂—CH₂)_(n)—OH, and H refers to 2-ethylbutyrate, 7refers to n-heptanoate, and 8 refers to 2-ethylhexanoate. Among otherknown plasticizers for polyvinyl butyral are dialkyl adipates havingaliphatic or cycloaliphatic ester residues, dialkyl sebacates,triorganophosphates, triorganophosphites, or phthalate plasticizers,such as benzyl butyl phthalate.

Since, on the other hand, excessively low adhesion makes it easier forglass fragments to separate from the PVB film, and thus increases therisk of injury to persons, particular industrial applications aim at acompromise between high and low adhesion, i.e. moderate adhesion, inorder to comply with both requirements—splinter binding and penetrationresistance—to the maximum extent. This applies in particular in the caseof laminated safety panes for vehicles, whereas laminated safety panesfor the construction sector are often intended to have relatively highadhesion between glass and adhesive film.

PRIOR ART

For the controlled lowering of adhesion of PVB film to glass, use haslong been made of the salts of alkali, or alkaline earth, metals withorganic acids, for example in the form of hydroxides, salts, orcomplexes, these being added in small amounts to the formulation duringthe production of PVB films (DE 15 96 902 B, DE 15 96 894 B, U.S. Pat.No. 3,249,488 A, U.S. Pat. No. 3,249,489 A, U.S. Pat. No. 3,262,835 A,U.S. Pat. No. 3,262,836 A). However, alkali metal salts, e.g. potassiumacetate or potassium formate, exhibit marked disadvantages in relationto the weathering resistance of open edges of the laminated safetyglass. Many salts have pronounced hygroscopic properties, and thispromotes an increase in the concentration of ingressive water at the PVBfilm/glass boundary, thus reducing the adhesion in the edge region ofthe laminated safety glass to the extent that the film can separate fromthe glass. Furthermore, alkali metal salts cause a visually unattractivewhite clouding of the PVB film at the points where it has exposure towater.

Salts of alkaline earth metals do not exhibit these disadvantages, andit therefore appears desirable to use these as antiadhesive agents.However, in combination with certain plasticizers these have thedisadvantage that the adhesion to the glass can be dependent on thethermal stress placed on the laminated safety glass. Variations in theadhesion can therefore arise, depending on the profile of pressure andof temperature in the autoclave process, the temperature and duration ofwhich can vary between one further processor and another, and betweenone production assembly and another. In particular in the case oflaminated glass production in the conventional autoclave process,adhesion can suddenly fall away sharply on long exposure to a highprocessing temperature, sometimes to zero under extreme processingconditions. This phenomenon is particularly observed when using certainplasticizers, namely glycol esters composed of oligoethylene glycols andof linear carboxylic acids, in combination with alkaline earth metalsalts as antiadhesive agents.

DE 24 10 153 C3 discloses a process for adjusting the adhesion ofplasticized partially acetalized polyvinyl alcohols using silanes havingsilicon functions and having organosilicon functions, where the silaneshaving silicon functions reduce adhesion and the silanes havingorganosilicon functions increase adhesion.

However, depending on the process conditions, the result of addingsilane compounds is occasional local crosslinking of the resin used,this crosslinking being difficult to control, and thus formation ofvisible nodules.

U.S. Pat. No. 3,841,955 A1 describes the use of organophosphates, e.g.tri-2-ethylhexyl phosphate, as plasticizers in a mixture with anothernonphosphate plasticizer. The amounts used are stated as more than 20%of the plasticizer mixture. No mention is made of any effect on theadhesion of the PVB film.

U.S. Pat. No. 4,681,810 A1 proposes the use of organophosphates in PVBfilm to provide self-extinguishing properties in the event of a fire.Organic phosphate is used because it has specific carbonizingproperties, and phosphites are used because they have “sequestering”properties. The selection of the amount of organophosphates is such thatit is a main constituent of the film. No mention is made of any effecton the adhesion of the PVB film.

U.S. Pat. No. 3,950,305 A1 describes the use of esters of phosphorousacid (phosphites) in a mixture with phenolic antioxidants with the aimof increasing the heat resistance of the PVB. The evaluation here usesyellowing due to ingress of oxygen and increased temperature, and thetorque curve in kneading tests. No mention is made of any possibleeffect on the adhesion of the PVB film. The minimum content of phosphitein the formulation for a film for a laminated safety glass is stated as0.6% by weight, based on the PVB used.

It is a well-known phenomenon that one and the same glass pane can givedifferent adhesion to the tin side and to the fire side, using one andthe same PVB film, but it is regarded as ideal for this difference to beminimized. This difference is attributable to the different chemicalcomposition of the two surfaces of float glass, the side known as thetin side—the side which in the float glass process is in contact withthe liquid tin—being tin-doped in the finished product. However, despitethe difference between the two sides of the glass, and also despite thefrequently encountered quality variations between batches and betweenproducers, the adhesion of a PVB film optimized for constant adhesionshould be independent of the orientation of the glass, and this meansthat the adhesion on the fire side should be as nearly as possibleidentical with the adhesion on the tin side.

OBJECT

It is an object of the present invention to provide a film based onplasticized partially acetalized polyvinyl alcohol for use asintermediate layer in laminated safety glass, which, on the one hand,has as uniform as possible adhesion to, respectively, the tin side andthe fire side in a laminate with float glass, and which, on the otherhand, gives uniform adhesion under different conditions of furtherprocessing. A further object of the invention is to provide a laminate,encompassing at least one silicate glass pane, and also a film based onplasticized partially acetalized polyvinyl alcohol, which complies withthese conditions.

It is a further object of the invention to eliminate adhesion decreasesin the finished laminated safety glass of more than 2.5 pummel units, asdefined hereinafter, even on exposure to extreme temperatures.

SUMMARY OF THE INVENTION

Surprisingly, it has now been found that alkaline earth metal salts oforganic acids in combination with certain phosphorus compounds canestablish stable adhesion which is less susceptible to thermaldegradation. Although the initial effect of addition of the phosphoruscompounds is to increase adhesion to the glass, counter measures via anincrease in the amount of alkaline earth metal salts or organic acidsestablish relatively stable overall adhesion at the level originallydesired with a pummel value of from ≧1.5 and ≦8.

Among the inventive phosphorus compounds are organophosphites, i.e.triesters of phosphorous acid with organic residues, and alsoorganophosphates, i.e. triesters of orthophosphoric acid with organicresidues.

These may in particular be symmetrical or asymmetrical alkyl phosphites,or symmetrical or asymmetrical alkyl phosphates, symmetrical meaningthat each of the three organic substituents linked by way of an oxygenatom to the phosphorus are identical, whereas in the case ofasymmetrical types at least two of the three substituents differ fromeach other.

The compounds may also be symmetrical or asymmetrical alkylarylphosphites or symmetrical or asymmetrical alkylaryl phosphates,symmetrical or asymmetrical aryl phosphites or symmetrical orasymmetrical aryl phosphates, or, respectively, mixed phosphites or,respectively, phosphates, which contain not only aryl substituents butalso alkyl substituents. In all cases, it is also possible for there tobe more than one phosphite or, respectively, phosphate unit linkedchemically via one or more organic radicals.

Examples of symmetrical alkyl phosphites are trilauryl phosphite ortristearyl phosphite.

An example which may be used for symmetrical alkylaryl phosphates istris(2,4-di-tert-butylphenyl) phosphite (obtainable, for example, asALKANOX® from Great Lakes Chemical Corporation) or tris(nonylphenyl)phosphite (obtainable, for example, as IRGAFOS® TNPP from Ciba).

An example which may be used for a symmetrical aryl phosphite istriphenyl phosphite (obtainable, for example, as IRGAFOS® TPP fromCiba).

An example which may be used for a mixed phosphite which contains notonly aryl substituents but also alkyl substituents is diphenyl octylphosphite.

IRGAFOS® P-EPQ from Ciba is a phosphite in which more than one phosphiteunit is linked chemically via an organic radical.

According to the invention, the film comprises not only the partiallyacetalized polyvinyl alcohol and a plasticizer, but also anadhesion-reducing additive in the form of alkaline earth metal salts oforganic acids. Use is made here of a magnesium salt and/or a potassiumsalt of organic acids. The amount to be used of the adhesion-reducingalkaline earth metal salt of organic acids depends on the PVB resinused, on the plasticizer, and on the desired pummel value, and ismoreover dependent on the organophosphite or organophosphate used. Theamount needed in practice therefore has to be determined via simpleexperiments. It is generally from 0.001 to 0.25% by weight, based on theentire film mixture. The preferred amount of alkaline earth metal saltsof organic acids is from 0.01 to 0.1% by weight if 3G8 (triethyleneglycol di-2-ethylhexanoate) is used as plasticizer, from 0.005 to 0.05%by weight if 3G7 (triethylene glycol n-heptanoate) is used asplasticizer, and from 0.005 to 0.05% by weight if DHA (di-n-hexyladipate) is used, based in each case on the entire film mixture.

The plasticized partially acetalized polyvinyl alcohol resin preferablycomprises from 25 to 45 parts by weight, and particularly preferablyfrom 30 to 40 parts by weight, of plasticizer, based on 100 parts byweight of resin.

The partially acetalized polyvinyl alcohols are prepared in a knownmanner via acetalization of hydrolyzed polyvinyl esters. Examples ofaldehydes which may be used are formaldehyde, acetaldehyde,propionaldehyde, butyraldehyde, and the like, preferably butyraldehyde.The preferred polyvinyl butyral resin contains from 10 to 25% by weight,preferably from 17 to 23% by weight, and particularly preferably from 19to 21% by weight, of vinyl alcohol residues. The polyvinyl butyral alsocontains, if appropriate, from 0 to 20% by weight, preferably from 0.5to 2.5% by weight, of acetate residues.

The water content of the films is preferably adjusted to 0.15-0.8% byweight, in particular to 0.3-0.5% by weight.

To test the adhesion of films based on plasticized partially acetalizedpolyvinyl alcohol, and to check the action of antiadhesive agents, useis made of what is known as a pummel test, certain variants of which aredescribed in the literature. A precisely defined, reproducible pummeltest is described below, so that the level of assessment can be adequatefor comparative purposes and for quantitative measurements. Wherever thedescription or the claims refer to a pummel test, this means a testdefined as follows:

Pummel Test

To test adhesion between a PVB film and glass, the film is laminated,using two panes of float glass of thickness 2.1 mm (PLANILUX®). A testspecimen with dimensions 8×30 cm is cut from the resultant laminatedsafety glass. This specimen is aged for at least 24 h in a freezer at−18° C. (±2° C.). The cooled test specimen is removed from the freezerand immediately “pummeled”, the specimen being conducted at a uniformrate underneath a hammer head which delivers blows of a precise position(weight 500 g, round head, energy of each hammer blow 1 Nm), in such away as to give about 75% overlap between one hammer blow and the next(FIG. 1). As shown in FIG. 1, the first blow has to make contact with acorner of the test specimen, and after that a complete row transverse tothe test specimen is traversed—symbolized by arrow 1 in FIG. 1—and onlywhen this process is complete is the adjacent row—symbolized by arrow 2)in FIG. 1, which then runs at a greater distance from the edge, to be“pummeled” in the opposite direction, until all of the glass to adistance of at least 6 cm, measured from the edge, has been shatteredand possibly separated from the film. During this procedure, the testspecimen must always lie flat with an angle of 5° with respect to asteel support mounted at an angle of 45° . The first hammer blow in thefirst row is indicated by A in FIG. 1, and the final blow in the secondrow is indicated by Z.

After completion of this procedure, the specimen is lightly tapped inorder to remove any loose glass splinters. For quantitativedetermination of the pummel value, a visual determination is made of theproportion of film surface exposed, and of the proportion still coveredby glass particles. The assessment takes place at room temperature. Forassessment of intermediate grades, the specimen is observed underincident light, and the amount of exposed film surface is determinedvisually. The detailed description of the pummel test procedure in thedissertation “A comparative analysis of PVB/glass laminate adhesiontests”; by Kristin Leah Kidd; University of Mass.—Lowell; 1993 may beutilized for supplementary information. Table 1 below is the basis to beused for evaluating the test specimen after the test, and for allocatinga number, which is the pummel value. These pummel values are from 0 to10, depending on the amount of exposed film surface.

The evaluation may award intermediate grades of 0.5 pummel units.However, the limited accuracy of the measurement means that finerdifferentiation is not sensible.

Table 1: TABLE 1 Pummel scale definition Amount of exposed film surfacein % Pummel value Separation of large-area −1 sections of glass 100 0 99 1  97 2  92 3  83 4  67 5  43 6  20 7  8 8  1 9  0 10

The pummel value −1 is given to laminated glass for which continuationof the pummel test becomes pointless because the first hammer blows leadto separation of large-area glass sections, due to almost total lack ofadhesion.

The Δ pummel tests described below are carried out in order todemonstrate that inventive PVB films with reduced adhesion have moreheat-resistance than a film which comprises the same PVB resin and thesame plasticizer in the same mixing ratio, and has been adjusted tocomparable adhesion, using an antiadhesive agent. 3 variants are used tosimulate heat stress, namely a standard autoclave process, additionalaging at an elevated temperature, and a long autoclave process, as canbe used in an extreme case of industrial manufacture of laminated safetyglass. Since the adhesion reduction in the PVB films of the prior art—ifit occurs—does not always take place with the same rapidity, this being,inter alia, a function of formulation, laminate production method, typeof glass and pretreatment of glass, and orientation of the glass withrespect to the film, the evaluation is in each case based on the worstresult from the 3 thermal stress variants, i.e. on the largest absolutereduction in the pummel value result, irrespective of whether it occurson the fire side or on the tin side.

The 3 thermal stress variants are to be carried out as follows: the PVBfilms are first bonded in a standard autoclave process—as describedhereinafter—using 2.1 mm glass. For “heat-aging” thermal stress, a testspecimen is then aged for 72 h at 125° C., vertically positioned in aheating cabinet. For the variant 3 “long autoclave process” thermalstress, the PVB films with 2 panes composed of 2.1 mm float glass arecombined in one of the usual processes, e.g. the roll process, to give apre-laminate, which is then adhesive-bonded in a long autoclaveprocess—as described hereinafter—to give the final laminate.

Standard Autoclave Process

The pre-laminates produced by one of the conventional processes known tothe person skilled in the art, and composed of two panes of glass and ofthe PVB film to be tested, are placed in a pressure autoclave, e.g. fromthe producer “Scholz”, designed for the production of laminated safetyglass, where they are secured vertically or approximately vertically ona suitable stand. The autoclave is designed so that temperature andpressure can be regulated independently of one another and can be keptconstant over a prolonged period. A pressure/temperature program is runwhich lasts 90 min in total, and is defined here as a function of time(start: 0 min, end: 90 min): starting from ambient temperature (about20° C.), the internal autoclave temperature reaches the maximumtemperature of 140° C. after 30 min, and this temperature then remainsconstant until 60 min, i.e. for 30 min From 60 min to 90 min, theinternal autoclave temperature is reduced from 140° C. to 40° C.

Starting from atmospheric pressure, the pressure is increased by 12 baruntil 20 min and kept constant at this value until 80 min, and is thenreduced back to atmospheric pressure by 90 min, i.e. by the end of theautoclave process. All of the changes in the parameters of pressure andtemperature here are to be made continuously, thus having a rampedheating and pressure curve. FIG. 2 gives a graphic representation of thestandard autoclave process.

Long Autoclave Process

The pre-laminates produced by one of the conventional processes known tothe person skilled in the art, and composed of two panes of glass and ofthe PVB film to be tested, are placed in a pressure autoclave, e.g. fromthe producer “Scholz”, designed for the production of laminated safetyglass, where they are secured vertically or approximately vertically ona suitable stand. The autoclave is designed so that temperature andpressure can be regulated independently of one another and can be keptconstant over a prolonged period. A pressure/temperature program is runwhich lasts 330 min in total, and is defined here as a function of time(start: 0 min, end: 330 min): starting from ambient temperature (about20° C.), the internal autoclave temperature reaches the maximumtemperature of 140° C. after 30 min, and this temperature then remainsconstant until 300 min, i.e. for 270 min. From 300 min to 320 min, theinternal autoclave temperature is reduced from 140° C. to 40° C., whereit is held for the remaining 10 min of the process.

Starting from atmospheric pressure, the pressure is increased by 12 baruntil 10 min and kept constant at this value until 320 min, and is thenreduced back to atmospheric pressure by 330 min, i.e. by the end of theautoclave process. All of the changes in the parameters of pressure andtemperature here are to be made continuously, thus having a rampedheating and pressure curve. FIG. 3 gives a graphic representation of thelong autoclave process.

Heat-Aging

For “heat-aging” thermal stress, a test specimen is first produced bythe standard autoclave process and is then aged for 72 h at 125° C.,positioned vertically in a heating cabinet.

Determination of Δ Pummel Values

6 individual pummel tests are carried out, in each case two (fire sideand tin side) for a laminate sample from the standard autoclave process,for a laminate sample from the long autoclave process, and for alaminate sample from the 72 h of heat-aging, and then a comparison ismade of the pummel value for the fire side from the standard autoclaveprocess with the other two pummel values for the fire side of theheat-stressed laminate samples, and the absolute value is determined forthe greatest difference of the measured pummel values. This maximumdifference of the measured pummel values for a film is the Δ pummelvalue for the fire side. The same procedure is to be followed for thetin side, and the maximum difference of the measured pummel values forthe tin side for a film is then the Δ pummel value for the tin side. Thelarger Δ pummel value of the two is then the “maximum Δ pummel value”for a film. This should be as small as possible, and always smaller thanor equal to 2.5. Values of 3 or more lead to adhesion variations beyondacceptable limits. According to the invention, the absolute value forall 6 of the measured pummel values is in the range ≧1.5 and ≦8.

In another, unexpected, effect found with the inventive addition oforganophosphites or organophosphates, adhesion on each of the two glasssurfaces, i.e. the fire side and the tin side, varies very little, anddifferences which are otherwise usual on the two sides are thereforereduced.

To produce the PVB films of the examples, the PVB powder is conveyedinto the feed section of an extruder, where it is combined with theplasticizer, in which the UV absorber, the antiadhesive agent, and theorganophosphorus compound, and also, if desired, other additives havebeen dispersed beforehand as homogeneously as possible, and is convertedinto a homogeneous melt which is extruded through a slot die to give afilm web.

BRIEF DESCRIPTION OF THE DRAWING

The invention is described in more detail below, using an example andthe drawing, in which:

FIG. 1 is a graphic illustrating the pummel test

FIG. 2 is a graphic showing the standard autoclave process

FIG. 3 is a graphic showing the long autoclave process

METHODS OF IMPLEMENTING THE INVENTION AND COMPARATIVE EXAMPLES

For the Inventive Examples 1, 5 and 7, and also the Comparative Examples2 to 4 and 6, all of which are listed below and shown in Table 2, filmsof thickness 0.76 mm were first produced in the manner known per se tothe person skilled in the art, as in EP 0 185 863 B1. To this end, amixture of commercially available PVB (Mowital® LP B 68/1 SF fromClariant) was homogenized and melted with plasticizer which is likewisecommercially available, namely 3G7 in Experiments 1 to 5 and DHA inExperiments 6 and 7, in a single-screw extruder, with a throughput of160 kg/h, and extruded through a slot tool. After appropriateconditioning, all of the films had the same water content of 0.47% byweight.

In Example 1, 0.04% by weight of a 30% strength magnesium octanoatesolution were added as antiadhesive agent to the parent mixture of 74%by weight of PVB and 26% by weight of the plasticizer 3G7, i.e. 0.12 gof magnesium octanoate were used for 1 kg of film mixture. 0.15% byweight of the organophosphite Alkanox® TNPP were added to provideconsistency of pummel values. As is seen in Table 2, the pummel valuesmeasured after the standard autoclave process were 5.5 on the fire sideand 5 on the tin side. The pummel values resulting from the longautoclave process, as defined above, were 4 on the fire side andlikewise 4 on the tin side. After 72 h of heat-aging at 125° C., asdefined above, the resultant pummel values were 3.5 on the fire side and5 on the tin side. This gives a Δ pummel value of 2 for the fire side, aΔ pummel value of 1 on the tin side, and a maximum Δ pummel value of 2.

From Comparative Example 2 it is seen that, without the inventive addedorganophosphite, firstly, and despite the smaller amount of antiadhesiveagent, 0.025% by weight of a 30% strength magnesium octate solution, thepummel values after the standard autoclave process are lower than thevalues in Example 1: 3.5 on the fire side and 3 on the tin side.However, each of the pummel values determined after the long autoclaveprocess is now 0, indeed −1 and 0 after the heat-aging (see Table 2),the resultant Δ pummel values therefore being 4.5 for the fire side and3 for the tin side. The maximum Δ pummel value of 4.5 leads to finalproduct values beyond the limits of acceptability.

Comparative Example 3 used the same antiadhesive agent content of 0.04%by weight (of the 30% solution) as Example 1, and the resulting pummelvalues from all methods of measurement are too low for practicalapplications. TABLE 2 1 2 (com- 3 (com- 4 (com- 5 6 (com- 7 Example No(inv) parison) parison) parison) (inv) parison) (inv) Polymer content: %by weight of PVB 74 74 74 74 74 75.5 75.5 Plasticizer: % by weight ofDHA — — — — — 24.5 24.5 Plasticizer: % by weight of 3G7 26 26 26 26 26 —— Antiadhesive agent: % by weight of magne- 0.04 0.025 0.04 0.015 0.050.02 0.08 sium octanoate (30% strength solution) Organophosphite: % byweight of Alkanox ® 0.15 — — — — — 0.15 TNPP Organophosphite: % byweight of Irgafos ® — — — — 0.08 — — DDPP Properties of laminate afterstandard (90′) autoclave program Fire side pummel value 5.5 3.5 1 6 6.53 3 Tin side pummel value 5 3 0 5 6 3.5 4 Properties of laminate afterlong (330′) autoclave program Fire side pummel value 4 0 −1 1 5 0 3.5Tin side pummel value 4 0 0 2.5 6 1.5 4 Properties of laminate afterheat-aging (72 h at 125° C.) Fire side pummel value 3.5 −1 −1 0 5 −1 2Tin side pummel value 5 0 −1 1 6.5 0.5 5 Evaluation Δ Pummel value, fireside 2 4.5 2 6 1.5 4 1 Δ Pummel value, tin side 1 3 1 4 0.5 3 1 MaximumΔ pummel value 2 4.5 2 6 1.5 4 1

In Comparative Experiment 4, the amount of antiadhesive agent wasfinally set so low, at 0.015% by weight (of the 30% strength solution)of magnesium octanoate, that the pummel values after the standardautoclave process are now again within the desired range, namely 6 onthe fire side and 5 on the tin side. However, the pummel value reducedto 1 on the fire side and 2.5 on the tin side after the long autoclaveprocess, and 0 on the fire side and 1 on the tin side after theheat-aging. The result is a maximum Δ pummel value of 6, which is beyondthe limits of acceptability.

Inventive Example 5 used an alternative organophosphite, namelyIrgaphos® DDPP, its amount being 0.08% by weight. In all of theexperiments, the resulting pummel values were very uniform, between 5and 6.5, giving a maximum Δ pummel value of 1.5, a very good value forpractical purposes.

Finally, Comparative Experiments 6 and 7 were carried out, using theplasticizer DHA, the addition of the antiadhesive agent being such as togive a pummel value of from 3 to 4 after the standard autoclave process.In comparison with the plasticizer 3G7, this requires considerablygreater amounts of antiadhesive agent. In the Inventive Example 7, using0.15% by weight addition of Alkanox® TNPP, all of the pummel values werevery narrowly distributed within the prescribed scope, the resultantmaximum Δ pummel value therefore being 1. Without the inventive additionof organophosphite, the pummel value reduces to values from 1.5 to −1,the resultant maximum Δ pummel value therefore being 4.

The invention is applied in the production of films for producinglaminated safety glass, in particular for applications in heconstruction sector and automotive sector.

1. A film based on plasticized partially acetalized polyvinyl alcoholfor use as intermediate layer in laminated safety glass, comprising from0.001 to 0.25% by weight, based on the entire film mixture, of one ormore additives which reduce adhesion of the film to a glass surface,these having been selected from the group consisting of magnesium saltsof organic acids, potassium salts of organic acids, and an additivecompensating for adhesion variations and comprising one or morephosphorus compounds selected from the group consisting oforganophosphites, i.e. esters of phosphorous acid with organic residues,organophosphates, i.e. esters of orthophosphoric acid with organicresidues, where the amount added of the phosphorus compounds is suchthat the pummel value, as defined in the description, of a laminatedglass produced using the film as intermediate layer, after the 90 minstandard autoclave process, after the 330 min long autoclave process,and—after heat-aging for 72 hours at 125° C. is >_(—)1.5 and <_(—)8 oneach of the two glass sides, and the maximum A-pummel value, as definedin the description, is <_(—)2.5.
 2. The film as claimed in claim 1,characterized in that the additive used which reduces adhesion of thefilm to a glass surface comprises magnesium 2-ethylhexanoate at aconcentration of from 0.001 to 0.2% by weight, based on the entire filmmixture.
 3. The film as claimed in claim 2, characterized in that theplasticizer used comprises 3G8, 3G7, and/or DHA, and in that the amountused of the magnesium 2-ethylhexanoate is from 0.01 to 0.1% by weight,if 3G8 is used as plasticizer, from 0.005 to 0.05% by weight, if 3G7 isused as plasticizer from 0.005 to 0.05% by weight, if DHA is used asplasticizer an appropriate intermediate amount of magnesium2ethylhexanoate, if use is made of a plasticizer mixture, based in eachcase on the entire film mixture.
 4. The film as claimed in claim 1characterized in that the additive used compensating for adhesionvariations comprises one or more phosphites from the group consisting oftris(nonylphenyl) phosphite, triphenyl phosphite and diphenyl octylphosphite in a concentration of from 0.05 to 0.5% by weight.
 5. The filmas claimed in claim 1 characterized in that the additive usedcompensating for adhesion variations comprises tris(nonylphenyl)phosphite, triphenyl phosphite and/or diphenyl octyl phosphite in aconcentration of from 0.1 to 0.2% by weight.
 6. A laminate, encompassingat least one silicate glass layer, and also a film as claimed inclaim
 1. 7. The use of phosphorus compounds, selected from the groupconsisting of organophosphites, i.e. esters of phosphorous acid withorganic residues, organophosphates, i.e. esters of orthophosphoric acidwith organic residues, as additive compensating for the variations inadhesion during further processing, in films based on plasticizedpartially acetalated polyvinyl alcohol.